Long Term Evolution (LTE) is a Fourth Generation (4G) wireless cellular communication technology. LTE adopts Orthogonal Frequency Division Multiplexing (OFDM) technology, and time-frequency resources composed of subcarriers and OFDM symbols form the wireless physical time frequency resources of LTE systems. Currently, OFDM technology has been widely applied in wireless communication. Due to the use of cyclic prefix (CP), CP-OFDM systems can solve the problem of multipath delay well and divide the frequency selective channel into a set of flat channels in parallel, which simplifies the method for channel estimation with a high accuracy. However, the performance of CP-OFDM systems is sensitive to frequency offset and time offset between adjacent sub-bands. This is mainly because the systems have a high spectral leakage, which is likely to cause interference between sub-bands. Currently, guard intervals are adopted in the frequency domain for LTE systems, but this practice leads to reduced spectral efficiency. Thus new techniques are needed to suppress out-of-band leakage.
Now companies are beginning to conduct research on 5G (fifth generation) wireless communication technology, in which suppression of out-of-band leakage is an important direction. Recently, new multi-carrier schemes, such as Filter Bank Multicarrier (FBMC) and Generalized Frequency Division Multiplexing (GFDM), introduced in some literature can suppress out-of-band leakage, but cannot meet the needs of different scenarios. In addition, there are compatibility problems with the OFDM technology of LTE, channel estimation problems, and problems of combining with Multiple Input Multiple Output (MIMO) technology. Although filtered OFDM (F-OFDM) and Universal Filtered Multi-Carrier (UFMC) mentioned in other literature are compatible with LTE, they have poor performance on suppression of out-of-band leakage, and need strict synchronization between sub-carriers within a bandwidth. That is, F-OFDM and UFMC are sensitive to frequency offset and time offset in the sub-band, and are degraded in the demodulation performance at the receiving end.
Therefore, it is necessary to propose a method to adapt to the needs of different scenarios. In addition, it is expected that compatibility with the LTE system to be maintained as much as possible, and the demodulation performance of the receiving end to be improved.